Technical Field
The present disclosure relates generally to the field of combustion furnaces and methods of use to produce glass, and more specifically to methods and systems to destabilize foam in glass handling equipment downstream of a submerged combustion melter.
Background Art
A submerged combustion melter (SCM) may be employed to melt glass batch materials to produce molten glass by passing oxygen, oxygen-enriched mixtures, or air along with a liquid, gaseous fuel, or particulate fuel in the glass batch, directly into a molten pool of glass usually through burners submerged in a glass melt pool. The introduction of high flow rates of oxidant and fuel into the molten glass, and the expansion of the gases cause rapid melting of the glass batch and much turbulence, and possibly foaming. Submerged combustion has been proposed in several patents and patents for application in commercial glass melting, including U.S. Pat. Nos. 4,539,034; 3,170,781; 3,237,929; 3,260,587; 3,606,825; 3,627,504; 3,738,792; 3,764,287; 6,460,376; 6,739,152; 6,854,290; 6,857,999; 6,883,349; 7,273,583; 7,428,827; 7,448,231; and 7,565,819; and U.S. Publication Nos. 2004/0168474; 2004/0224833; 2007/0212546; 2006/0000239; 2002/0162358; 2009/0042709; 2008/0256981; 2008/0276652; 2007/0122332; 2004/0168474; 2004/0224833; 2007/0212546; 2011/0308280; and 2012/0077135. Certain SCMs and/or flow channels may employ one or more high momentum burners, for example, to impinge on portions of a foam layer. High momentum burners are disclosed assignee's patent application U.S. Ser. No. 13/268,130, filed Oct. 7, 2011. “High momentum” combustion burners means burners configured to have a fuel velocity ranging from about 150 ft./second to about 1000 ft./second (about 46 meters/second to about 305 meters/second) and an oxidant velocity ranging from about 150 ft./second to about 1000 ft./second (about 46 meters/second to about 305 meters/second).
Often it is a primary goal to melt batch or other feed materials in an SCM as quickly and with as small a footprint SCM as possible. Although this is still desired for the most part, one drawback to this strategy in known submerged combustion systems and methods of melting glass-forming materials using an SCM is the tendency of the foam formed in the SCM to be resistant to destruction or even reduction. This may cause one or more problems in equipment downstream of the SCM, for example, glass conditioning and transport may be hindered as the foam layer may serve as an insulator and may limit the amount of energy capable of being transferred to the molten glass to maintain its temperature. Foam found in (or on top of) glasses typically exists as stable tetrahedral bubbles which need an outside influence to de-stabilize them and therefore break the foam, allowing heat transfer into the glass from burners located above the glass line. In addition, the foam may be destructive of forehearth heating systems and construction materials. In extreme cases, the foam may cause systems to require shutdown, maintenance and may result in a process upset. Attempts to reduce the foam through process adjustments, summarized in “Glass Industry of the Future”, U.S. Dept. of Energy, Report 02-GA50113-03, Sep. 30, 2008, such as use of helium and steam to scavenge and consolidate bubbles, sonic methods to consolidate bubbles, vacuum to increase bubble size, and centrifugal force have not met with complete success in reducing foam to an acceptable amount.
It would be an advance in the glass manufacturing art if foam produced during submerged combustion melting of glass-forming materials could be de-stabilized, reduced, or even completely destroyed in equipment downstream of the SCM.